The MP7 is a remarkably compact weapon. It is less than 15 inches long, and fires only a 4.6 mm cartridge. In addition, the weapon weighs only four pounds with a full load of ammunition. It is marketed partly toward undercover police forces which need substantial firepower to be easily concealable. Despite its size, the MP7 is capable of penetrating modern body armor. (Specifically, it was tested against body armor worn by former Soviet Blocspecial forces.)

The MP7 is also designed for versatility. Despite its short length, the barrel is more than 7 inches long. It is made largely of carbon fiber, which allows it to be stripped in seconds. Also, it is completely ambidextrous, with all controls (trigger, safety, fire selector) accessible from a left- or right-handed position.

source: http://www.hk-usa.comH&K's American website provides only Imperial units, and the MP7 is lacking from the European and German sites. Therefore, all metric units (except calibre) have been clumsily converted by Syntari.